Diesel Reforming for Solid Oxide Fuel Cell Application - OSTI.gov

Diesel Reforming for Solid Oxide Fuel Cell Application Di-Jia Liu, Shuh-Haw Sheen, & Michael Krumpelt SECA Core Technology Peer Review Workshop Tampa, FL January 27 - 28, 2005 Argonne National Laboratory A U.S. Department of Energy Laboratory Operated by The University of Chicago

The Critical Issues in Diesel Reforming Catalyst & Catalytic System Development Catalyst Cost -

•

Costly Rh usage Support Collapse

Efficiency & Selectivity Fuel property & chemistry

Catalyst Deactivation

Durability -

Metal vaporization & agglomeration Support stability Sulfur poisoning Coke formation

System

• •

C-deposit

Activity -

•

S poisoning Agglomerating S S S S

Fuel injection & mixing System integration

Reforming catalyst aging – an example 14

H2 yield (mol/mol-fuel)

•

Vaporizing

12 10 8 6 4 2 0 0

20

40

60

80

100

Time on stream (hr-1) 2 Pioneering Science and Technology

Argonne National Laboratory

Diesel Reforming Catalyst Development

3 Pioneering Science and Technology


What Constitutes an Ideal Diesel Reforming Catalyst?

• • • • • •

Atomically dispersed active site. Stably anchored over the support surface. Effectively cleaving C-H, C-C & C=C bonds through oxidative process. Competitively releasing hydrogen over oxidation to H2O. Competitively oxidizing surface carbon over C=C bond growth. Minimum chemical binding energy with sulfur.



Objective: Developing Perovskite Based ATR Catalyst •

The Perovskite Catalyst… - Low cost material. - Stable under high temperature & redox environment. - Exchangeable A & B sites lead to ionic dispersion & improve catalytic activity. ucture ABO 3 Str e it k s v Pero

CxHy

B A

CO, CO2 H2

H2O, O2

H2

e-

e-

Redox Cycle Conductivities of both e- and VO¨ of perovskite enhance catalytic active site through electron & oxygen vacancy transfers in a redox process. Pioneering Science and Technology

5


Approach: ANL Perovskite Catalyst Materials

• • • •

Perovskites include chromite, aluminite, manganite, ferrite, … Self-combustion synthesis (Pechini method) B-site doped with Ru, Rh, etc… A-site exchanged with La, Sr, Ba, Gd, Ce, Pr, …



Catalyst Activity Study: Test Apparatus & Conditions •

Fuel -

•

Temperature -

•

Reactor: 700 °C to 800 °C Preheating: 200 °C.

Input Mixture -

•

Alkane surrogate - C12H26 Organic sulfur - Dibenzothiophene (50 ppm S) Other HC surrogates – Monoaromatics, Polyaromatics, Cycloparffins …

ATR: O2/C = 0.3 ~0.5, H2O/C = 1 ~ 3

Space Velocity -

Fuel Flow Rate = 2.8~5.0x10-3 gfuel/gCat•sec GHSV = 50 K ~ 100 K hr-1

Diesel Reforming Catalyst Test Plant 7 Pioneering Science and Technology


Catalyst Activity Study: Test Plant



Catalyst Activity Study: Investigation on ATR Catalytic Light-Off for Perovskite Material 1.0 0.9

reforming

oxidation

Product Yield, mL/min

0.8

H2O

0.7

H2

0.6 0.5

O2

0.4 0.3

CO C4H10

0.2

CO2

0.1 0.0 100

200

300

400

500

600

700

800

Temperature ( o C)

Ru doped perovskites demonstrate low light-off temperature for hydrogen production suitable for SOFC application Pioneering Science and Technology

9 Argonne National Laboratory

Catalyst Activity Study: Basic Performance Parameters in Catalytic ATR Reforming Chemical Reactions in Diesel ATR Reforming: CnHm + xO2 + yH2O = nCO2 + (m/2 + 2n –2x)H2 + (y + 2x -2n)H2O An example:

C12H26 + 6O2 + 12H2O = 12CO2 + 25H2

Definition of Reforming Performance: H2 yield = CH2/ Cfuel Reforming efficiency = {CH2∆HcH2 + CCO∆HcCO}/ Cfuel∆Hcfuel COx selectivity = {CCO2 + CCO}/ nCfuel Ci = Molar flow of i, ∆Hci = Heat of combustion of i, n = Number of C in fuel molecule 10 Pioneering Science and Technology


Catalyst Activity Study: Benchmarking New Perovskite Materials with Rh-Based Catalyst Performance of a selected group of perovskites 100

100%

80

80%

60

60%

40

40%

20

20%

i rN

r

Sr C

La

Sr C La

M

nR

u

u La

lR

La

A La

A Sr

Pr Fe R

u

u lR

u rR La

P

dC G

rC

rR

h rR

u

Sr C

La

La

C

rR

rR Sr C La Pioneering Science and Technology

u

0% u

0

COx Selectivity (%)

Reforming Efficiency (%)

benchmark

ATR input O2/C = 0.5 H2O/C = 2

11


Sulfur Tolerance Study: Recoverable Activity over Perovskite Materials

S 4-MDBT S


DBT

100

100%

80

80%

60

60%

40

40%

20

20%

COx Selectivity

Introducing 50 ppm sulfur in the form of DBT temporarily suppress reforming efficiency and COx selectivity.

Dibenzothiophene (DBT) and its derivatives are difficult to be removed from diesel through HDS process …

4,6-DMDBT S

0 0

50

100

150

200

250

300

350

0% 400

Time-online (min)

Catalyst re-activates after S is removed from fuel. 12 Pioneering Science and Technology


Sulfur Tolerance Study: Resistance to Poisoning Improves at Higher Operating Temperature 100

T = 700 °C

b/f S-fuel

T = 800 °C

b/f S-fuel

a/f S-fuel


80 w/ S-fuel a/f S-fuel

60

w/ S-fuel

40

20

0

Catalyst = LCR-800, O2/C = 0.5, H2O/C = 1.0, GHSV = 130,000 hr-1

Increase reaction temperature by 100 °C significantly improved catalytic performance in the presence of sulfur 13 Pioneering Science and Technology


Sulfur Tolerance Study: Stable Reforming Observed during 100-Hr Aging Test with 50 ppm S in DBT 100%

80

80%

60

60%

40

40%

20

20%

0

0% 0

20

40

60

80

100

Time (hour) Reforming Efficiency (%)

COx Selectivity

120

T = 800 °C Fuel = 50 ppm S/C12H26 GHSV = 50,000 hr-1

Excellent catalytic stability was observed during 100 hour aging test with S contaminated fuel Pioneering Science and Technology

COx Selectivity


100


Coking Prevention Study: Issues with Heavy Hydrocarbon Components in Diesel Compound Type

Wt% Analysis, ANL

Wt% Analysis, Exxon

Ave. or Ref. Formula (ANL)

Paraffins

38.7

39.7

C16 H34

Cycloparaffins 1-ring cycloparaffins 2-ring cycloparaffins 3-ring cycloparaffins

29.6 11.5 4

23.6 20.6 6.5

C10 H21 C16 H32 C22 H38

7.3 3.2

3.2 0.9

C8 H8 C12 H16

Mono-aromatics Alkyl benzenes (a) Naphthenebenzenes (Indans (b) + Tetralins (c) + Indens (d)) Di-aromatics Alkylnaphthalenes (a) Acenaphthenes (b)/Biphenyls Acephthalenes (c)/Fluorenes (d)

Representative Molecular Structures

(c)

(a)

(b)

(d)

(a) 1.8 3.5 0.3

1.6 2.2 1.7

(b)

C13 H14 C9 H12 C13 H10

(c)

(d)



Coking Prevention Study: Correlation b/w Efficiency & Residual HC’s Formation from Diesel Components 1

80

Unconverted HC (excld CH4)

0.1

60 0.01 40 0.001

20

e en

e

Fuel blends with Dodecane

5%

M

%

et hy

Bu

ln

ty

ap

lb

ht h

en z

al

en

lin tra Te % 10

ty Bu % 40

10

lc y

%

cl o

D

he

ec

xa

al in

ne

0

20

do de ca ne

0.0001


100

Coking is affected by Temperature, O2/C, H2O/C, Catalyst & CATALYSIS CHEMISTRY of HYDROCARBONS. 16 Pioneering Science and Technology


Coking Prevention Study: Deactivation Mechanism & Coke Formation by Polyaromatics •

•

Impact on ATR reforming by 1methylnaphthalene (1MN)

80

700 °C

800 °C

-

40

8

20

Residual HC's (%)

12

Efficiency (%)

60

16

Proposed Model of PAH impact on Reforming and C-formation Low cetane# / high Tig make them hard to oxidize. Competition b/w oxidation vs. C growth H2 CO CO2 H2O

HC’s

4

O2 Add 5% 1MN 0 0

100

200

300

400

0 500

Time (min)

1MN tentatively deactivates reforming. Activity recoverable after 1MN removal. Performance improves a higher T. O2/C & H2O/C have limited impact. Pioneering Science and Technology

Long resident time and slow decomposition of PAH over active site reduce reforming rate & increase residual HC’s & coke formation! 17 Argonne National Laboratory

Coking Prevention Study: Fishbone Analysis on Root Cause of Coking

ox i ca da t a tio ly n st ac s ti vi ty

High HC residues, C2, C3, C4…

Coking

Lo w

Su l fu

rp oi so ni ng

re tu ra pe m te s si ly ta ca O w H2 n Lo & atio O 2 tr w en of Lo nc n co tio s i ics po at m m co aro de vy a ow e Sl h al t e M

ss o l

Incomplete C-C bond breaking & oxidation

We are currently working on coking reduction through both catalyst & engineering improvements 18 Pioneering Science and Technology


Catalyst Characterization: Identifying Perovskite Structure & Ru Active Site Conventional (XRD, SEM, ICP, TPR, BET…) and Advanced (EXAFS, XANES) characterization methods were used to study structure-activity relationship XRD confirms perovskite structure

EXAFS reveals Ru embedded in perovskite

LaSrCrRu 3 FT(χ(k)*k )

* Intensity (counts)

0.24

A B O

0.18

0.12

0.06

0

LaCrRu

1.5

3

4.5

6

R [Å]

10

30

50

2 th e ta Pioneering Science and Technology

N

R (Å)

σ2

LCSR1200

6.0

1.943

2.5x10-5

LCSR800

4.7

1.953

2.5x10-5

LCR800

4.3

1.962

1.0x10-5

70


Summary: Knowledge Gained on Perovskite Catalyst & Its Applicability to SECA • • • •

Ru doped perovskites demonstrated excellent catalytic reforming activities comparing with Rh based catalysts. Active catalysts are the perovskites containing Ru at B site with oxygen vacancy and high surface area. Improved sulfur tolerance and perovskite stability were demonstrated through 100-hr aging at higher operating temperature. Root cause of catalyst deactivation through coking by aromatics was identified. Improvement through catalyst material refinement and new reactor engineering approach is underway.

Perovskite ATR catalysts provide new low-cost alternatives in fuel reforming for SECA. 20 Pioneering Science and Technology


Diesel Fuel Mixing & Cool Flame Study



Critical Issues in Fuel Mixing Diesel Air

• • •

Recyc. Exhaust

Completed vaporized fuel is essential for catalytic reforming. Diesel fuel cannot be evaporated without fractioning. Incomplete mixing creates “hot spots” on the catalyst and leads to sintering & coke formation.

reformate 22 Pioneering Science and Technology


ANL Approach: Diesel Injection Technology Improvement & Pre-reforming through Cool Flame •

Diesel Injection – A joint effort between ANL and International Truck and Engine Corporation (ITEC) - ANL is currently building a test facility for air-steam-fuel-exhaust gas mixing study with catalyst testing capability for ANL autothermal reforming process. - ITEC provides diesel-fuel injectors and fuel-injection control system

•

Cool Flame – An alternative method to further improve fuel mixing and pre-reforming. - What is cool flame? - How it may benefit SECA fuel reforming effort? - Our approach – Investigating operating condition and gas composition in cool flame.

L. Hartmann, K. Lucka, and H. Kohne, 2003 23

Pioneering Science and Technology


Diesel Mixing Study: Fuel-Air-Steam Mixing Facility Under Construction High Pressure Engine Oil Accumulator Oil Filter

H Water Reservior

Pressure Multiplier Injector Control Module

LP N2 Tank

Pressure Regulator

Diesel Fuel

T

HP N2 Tank Fuel Filter

Valve

Fuel Heater

Fuel Injector

Valve Humidity Sensor Temperature Sensor Pressure Sensor

Pre-heated Air Compressed Air

Mixing Chamber PTH

Sapphire Window

6”-4” Reducer Diagnostic Chamber

Purge N2 P T H Data

Data

PC

Cooling Air

Solenoid Valve Valve Control Pulse Trigger P T H Control

Exhaust Gas Outlet (to outdoor) Blower Disposal Tank

Mist Trap

Exhaust Gas from Hood 24



Diesel Mixing Study: ITEC Diesel Fuel Injector

• Pulsed injection with pulse rate of 10 ~ 70 Hz (500 ~ 4000 rpm for 4-cylinder engine) • Injection duration Below 1 ms at idle to 20 ms at high load • Injection nozzles 6 holes around • Fuel injection rate Peak : Idle :

105 mm3/stroke at 240 bar and 600 rpm 9.2 mm3/stroke at 45 bar and 600 rpm 25



Diesel Mixing Study: Demonstration of Fuel Injection Test Chamber



Acknowledgements •

This work was supported by the U.S. Department of Energy, Office of Fossil Energy – Solid State Energy Conversion Alliance (Program Coordinator - Wayne Surdoval, Program Manager - Norman Holcombe) and Office of Energy Efficiency and Renewable Energy – FreedomCAR & Vehicle Technologies (Program Manager - Sid Diamond).

•

Thanks to the technical support by - Cécile Rossignol - Mike Schwartz - Hual-Te Chien - Jameel Shihadeh - Martin Bettge - Jeremy Kropf 27 Pioneering Science and Technology
